[cornishpixels]

You can always take a multi-tenant system and convert it into a single-tenant system a lot more easily. First and foremost, you can simply run the full multi-tenant system with only a single tenant, which if nothing else enables progressive development (you can slowly remove those now-unnecessary WHERE clauses, etc).

[krainboltgreene]

> You can always take a multi-tenant system and convert it into a single-tenant system a lot more easily.

This is not true if your primary keys are int or bigint.

It's also not true if you have any sort of unique indexes that are scoped to a table.

[cornishpixels]

How is it not? Uniqueness would cease to matter between different tenants. They're unique by virtue of using a different database.

[ehsanu1]

I think you are talking about problems going from multiple single-tenant systems to a single multi-tenant system. You parent is talking about the opposite.

[gomox]

True, but:

In my experience by the time you reach this point you have a lot of operational complexity because you and your team are used to your production cluster being a single behemoth, so chances are it's not easy to stand up a new one or the overhead for doing so is massive (i.e. your production system grew very complex because there is rarely if ever a need to stand up a new one).

Additionally, a multi tenant behemoth might be full of assumptions that it's the only system in town therefore making it hard to run a separate instance (i.e. uniqueness constraints on names, IDs, etc).

[egamirorrim]

Some of the issues I see in one of my projects is high interactivity between accounts. E.g. if account 1 'sends' something to account 2 both of the shared/separate db instances need to be up or there'll need to be some kind of queueing mechanism.

That's hard enough and then add to it that most clients want to BYOK to those instances